1. Field of the Invention
The present invention relates to a method and apparatus for providing an improved content delivery system for use with an interactive information distribution system. More particularly, the invention relates to an improved system for allocating, storing and distributing information within a video on demand (VOD) system.
2. Description of the Background Art
Recent advances in digital signal processing techniques and, in particular, improvements in digital compression techniques, have led to a plethora of proposals for providing new digital services via existing telephone, coaxial cable and satellite data networks. For example, it has been proposed to provide hundreds of cable television channels to subscribers by compressing digital data and digital video, transmitting the compressed digital signals over conventional coaxial cable television channels, and then decompressing the signals in the subscriber's receiver.
Another application for this technology is a video-on-demand (VOD) system in which a subscriber communicates directly with a video service provider via telephone lines to request a video program from a video library. The requested video program is then routed to the subscriber's home via telephone lines or via coaxial cable television cables for immediate viewing.
The VOD system may use a frequency multiplexing technique to enable control information for a subscriber's receiver to be transmitted through a cable network back to an information server. Such a system permits bi-directional communications over a single network. In addition, graphical menus are displayed upon the subscriber's television and by using a remote control device, a subscriber selects a desired program for viewing.
Many VOD distribution systems established by the service providers utilize a plurality of cable “head-ends”, where each head-end serves as a distribution point for a respective “neighborhood” of subscribers.
Each head-end comprises one or more VOD server systems. Each VOD server system contains subsystems that interface with each other to manage, store and distribute video content. The subsystems usually are composed of a video stream server, primary and secondary data storage units, and host workstations on which various management software applications execute.
The subscriber has thousands of video titles from which to choose. A subscriber selects a video title displayed on their monitor and a signal is sent from the subscriber's location to the local head-end server. The software management applications, for each of the local video stream servers, queries a database to inquire if the chosen content is presently stored at the head-end storage devices. The most popular video content is typically stored locally on the primary storage device. The secondary storage device is typically a large library of the remaining video content.
If the content is present at the head-end, the server will deliver the video package to the subscriber. Alternatively, if neither storage devices at the head-end have the selected video information, the head-end must first retrieve the requested content from the service provider before delivery. Because of this deficiency, there is a delay in transmission of the video information to the subscriber.
Head-ends that are networked together are known as regions and as such, are served by several VOD systems. The service provider, through a managerial software application, controls the introduction and removal of video information to and from these servers. Thus, each region has a plurality of servers and storage equipment, with each head-end having duplicate video content stored therein.
All of this additional storage capacity, in the form of additional storage hardware results in higher system costs. These costs are primarily due to procuring and maintaining reliable storage devices. This in turn increases the cost of building infrastructure and subsequently, the ultimate cost to the consumer.
Thus, there is a need to reduce the cost of implementing and maintaining replicated head-end located storage libraries, while still maintaining the quality and quantity of video titles offered by the service provider. To achieve this, there is a need to support low latency file transfer operations at relatively high but variable rates using a variable bit rate (VBR) transport, support high quality streaming transport at various control bit rates, as well as supporting appropriate control message flows.